This invention relates to heat transfer mechanisms, and more particularly to an improved heat transfer mechanism for removing heat generated from high powered integrated circuit devices.
A basic approach for cooling semiconductor devices is using a liquid for removing heat. A liquid cooling approach is to conduct heat from the device through a solid conductor, such as a piston or the like, that is in contact with both the device and a liquid cooled cold plate. Such a system is described in U.S. Pat. No. 4,245,273. An improvement is described and claimed in U.S. Pat. No. 4,312,012, wherein liquid is circulated through fins and elements that actually contact the backside of the devices. The cooling liquid is carried to the devices with flexible conduits.
Liquid cooling allows very high cooling density. Unfortunately, it tends to be expensive. It requires plumbing and a pump. If a cold water source and warm water drain are not available, then the system must also include a chiller to transfer the heat to an air stream. Liquid cooling often involves water, which requires design effort to prevent it from contacting and corroding the electronics.
Air cooling offers better economy. However its cooling performance is limited. Air has a low density times heat capacity. Therefore, substantial cooling requires substantial air flow. For most heat sinks, this requires substantial air speed, fan pressure, and noise. Conversely, allowable noise and fan pressure often limit air cooling, especially for a large module with many densely packed chips.
Another problem with air cooling is that as the air passes over a length of cooling fins it becomes hotter. Thus, the degree of cooling is not uniform over the surface of the substrate supporting the devices. Systems for air cooling of semiconductor devices are shown in U.S. Pat. Nos. 3,961,666, 4,489,363 and 3,843,910. An improvement in forced air cooling is provided with "impingement" cooling. This system forces air directly downwardly against cooling studs or fins attached to a cooling plate. Impingement cooling systems are shown in U.S. Pat. Nos. 4,296,455 and 4,620,216.